Filter elements used in industrial systems to remove the impurities from fluids that are used in the ongoing operations are known from a number of prior art embodiments. For example, EP 1 015 095 B1 shows an advantageous design that has become very popular and is used extensively in pertinent systems. If in operation the filter mat becomes completely clogged with impurities, the filter element has to be changed for a new and unconsumed filter element. In light of the extensive use of such filter elements, having a large quantity of filter elements is required for the initial setup and replacement. Such filter elements can be referred to as “mass produced articles.” Hence, a simple and efficient production of the filter elements is of considerable economic importance.
According to the state of the art described in document EP 1 015 095 B1, the filter element is provided with an outer sleeve made of a perforated film web and is produced such that a closed cylinder is made of a film web forming the outer sleeve. In this case, the overlapping ends of the film web are connected by a longitudinal weld. Then, the annular body is introduced into the cylindrical outer sleeve. To facilitate the introduction, the pleats are gathered together at the frontal end of the annular body such that the result is an insert cone that facilitates the introduction into the cylindrical outer sleeve.